You can now download the APK for JW Library from jw.org.
This is great for those who can't use a store for downloading app. You could find it elsewhere from a website that hosts apks, but I never know whether you could trust these, might contain malware. Now you can get straight from the source.
Lately I have been using an android e-ink reader (I find it easy on the eyes), mainly for PDFs. However JW Library works just great with it, a little slow on the screen refresh, but for reading its great.

The icons are now the same as the WOL. The way the research guide is included is the same as in the WOL as well. I wonder if we will get the indexes at some point. All part of unifying the apps and websites. But I suspect this is just one stage in the unifying process, and we will see another update (v12) before it is complete.

I tried it with some other publications. For example, you have downloaded the videos for the Pure Worship book. Now if delete that book, all those videos are also gone.
But then I tried this with the Good News brochure, and all the videos remained.
In some ways I can understand this, but it means for publications like the MWBs and WTs it could mean deleting videos you don't want to.
On the other hand, there is some good news for sound servants downloading videos for the meetings
You can now go to Publications > Meeting Workbooks > go to the workbook and then click on Download Media, and download all the media for that month in one go.

I have seen this before with updates. I think it is because the base update is now larger than 2gb, a bug in the calculations affects the download progress and when it reaching 2gb it seems stuck at 99%, when in fact there is much more to download. In reality 2gb when it reaches 2gb it should only by about 50%.
I think it is time to refresh the ISO to the 2019 edition. Most of the files are replaced by the update package.
Personally I would have a basic library app with no publications installed. Then you download the publications as a separate package. Also because the videos are such a large part of package, I would have two options, one with videos, one without to save data. You may already have the videos, so why download again?
Another option would be split the library according to the indexes, one for 1950-1985, and another for 1986 to today. If you have no need for the older publications, you could save data by not downloading them. I rarely look at anything before 1986 anyway. These are just my own opinions.

This link will download the base update package that will update from 2017 (as provided on DVD or ISO) to the 2019 version. It is almost 4gb
http://download-a.akamaihd.net/meps/wtlibrary/WTLibrary/E/WTE/WTLibrary.E.WTE.1901.BASE.UPDATEPKG
Next, for the latest updates
http://download-a.akamaihd.net/meps/wtlibrary/WTLibrary/E/WTE/WTLibrary.E.WTE.1902.UPDATEPKG

It depends on the system you use. We currently use KHConf and that has a limit of 18 callers. If that was constantly used to the full and ones who really need it (housebound publishers for example) were being rejected by the system, then it would be unfair to those ones. So while no need to monitor, it is still best to keep some sort of control over it.
Also it is still good to check in on who is using the system. Are publishers using it to avoid going to the kingdom hall? There are those who can't go, and these link up systems are great for them. And then there are those who don't want to go. It is not what it is for, and they may need some spiritual help.

Do you think the revised website and JW Library app will be released at the same time, or will one before the other?
Also, I was thinking that the revised app will have a different way of navigating around it. Something to keep in mind if you use it for the your KH sound system. But may require getting used to or a little re-training. You can stop the Microsoft Store from automatically updating apps from the store app settings.

I like the Watchtower Online Library as it is now and use it a lot. Its my preferred digital library of choice over the other two. I've never been a fan of change, and "If its not broken, don't try to fix it". I know there is / has been a lot of planning and designing going into the new format of jw.org. I hope it will be just as good and easy to use, or better. And that you can still access the library part in a similar manner.
It was only a matter of time that they stop producing annual DVDs of the WT Library. They haven't updated the ISO download yet, still on 2017. Recently installed it on someone's PC - 2GB for ISO, then 3.4GB for the "1901 base update", then a bit more for the 1902. A lot of downloading!!

This is the announcement about the changes
https://www.jw.org/en/whats-new/new-publications-revised-websites-apps/
Additionally, the JW Library app will be redesigned to incorporate the content and features of Watchtower Library as well as content that now appears only on the jw.org website. The overall appearance of the new website and the new app will be unified and become even more user-friendly. For example, to ensure that the redesigned website and app are not too hard to navigate, key aspects will be simplified to help users find spiritual food quickly.
While I, like many of the sound operators, would like to see new features in JW Library to help at the meetings, there is no mention of any feature like that being incorporated. The main focus at the moment seems to be is to unify and make more user-friendly. Some content from jw.org is already available in JW Library in the Publications > Articles Series, although only recent articles, not the back catalogue going back to the website launch of 2012. Can we expect to download articles from the Newsroom as well into JW Library?
I also honestly think that once the all content from Watchtower Library is transferred to JW Library, then it will be gradually phased out, leaving the unified jw.org website and the JW Library app.

I think it would be hard to compare since this is the first official PDF of the Insights released through the organization. Any older ones were unofficial, made through scans.
Updates made due to refinements of understanding would have been previously discussed in the publications, primarily the WT. There would be nothing new hidden in there.

If its a single pole switch, and wired reverse polarity, then you will be switching the neutral, not the live or line feed. A double pole switch will switch on/off both live and neutral.
Lights if reversed, means you light switch could be switching the neutral and not the live. Why its always best to check with a tester before you undertake any maintenance, as what you think is off, could actually be on.